Light weight Concrete


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Old 09-19-05, 06:48 PM
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Light weight Concrete

I want to pour a floor over some in floor heating tubing; the floor will be two and a half inches thick. I thought about using lightweight concrete. Can any one mix this? Does anyone know what the ingredients are? Would grepcrete be better for the job than lightweight concrete?
 
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Old 09-19-05, 06:56 PM
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Light weight Concrete

Either Gypcrete or lightweight concrete can be used. The cost will depend on the local market. Typically, lightweight concrete is heavier, stronger and will take more abuse. Usually the same sturcture systems will adequate for both because of the thin thickness.

The extra weight of the lightweight may be an advantage comfort-wise.

You can mix the lightweight concrete youself if you have a local source for the lightweight aggregate. The aggregate is usually sold only to concrete producers because of the volumes required for economic handling & shipping. Concrete block producers are some the the largest users of lightweight aggregate, so you may be able to buy a small amount from one.

Dick
 
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Old 09-19-05, 07:05 PM
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Does the lightweight weigh more than the gypcrete? For the comfort wise does the lightweight give off more heat than gypcrete?
Thanks for the information
 
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Old 09-19-05, 08:17 PM
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Light weight Concrete

I beleive lightweight concrete weighs more. Gypcrete can have a more variable density.

They both give off the same amount of heat since you are putting as much heat into the floor system. There is no real heat loss since you will have a conditioned space below or an insulated slab below, so it is not a question of insulation.

A heavier material will hold the heat longer or have the property of thermal inertia, with evens out temperature swings. This is one of the reasons a heavy structure can be more comfortable.

Both are close to the same weight so there is little difference.

Dick
 
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Old 09-20-05, 06:35 PM
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Thanks for the information I will probally pay through the nose for two and a half yards of lightweight, and we will probally pump it up to the second floor where I need it. The lower level we can wheel and use a regular mix.
Thanks again
 
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Old 09-22-05, 02:31 PM
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Are you sure your joists were engineered for that much weight? Even lightweight concrete at 2 inches thick will weigh close to 16 lbs per square foot. Combined with any furniture, etc. you will have, it could be a lot of weight. Just something to consider.

Pecos
 
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Old 09-22-05, 07:12 PM
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The room is 14 feet wide. I am using 2x10, 16 inches on center and every other 2x10 is a double. I just remeasured the floor depth and it looks like I will have 2 inches of concrete or gypcrete and 3/8 inch of tile on top of that. I though that floors were designed to hold 40 pounds to the square foot so I hope I am ok. Unless I did the math wrong (and math is not my best subject) I will need one and a third yard of concrete. If concrete weights 3000 LB's to the yard that would make it weight 16 or 18 pounds to the square foot (I got 18 LB's to the foot), but that is not lightweight. Lightweight might weigh half or a little better than half of regular concrete. I am pretty sure I will be ok.
 
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Old 09-22-05, 08:19 PM
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Light weight Concrete

Last I checked, lightweight concrete had a maximum dry density of 115 pounds per cubic foor. It can be less, especially if it does not have to be structurally loadbearing. It still will be solid enough for any tile application.

Some of the expanded clay aggregates (Arkalite and Gravelite) can be used to make lightweight concrete. They both are widely available and have very good technical support for engineers and concrete producers. If your concrete supplier uses one of these he may be able to get mix designs for concrete lighter than 115 pcf. Both aggregates are commonly available in the south and near the Mississippi and Ohio rivers (within 100 to 200 miles or so) and in the Chicago area. The aggregate is delivered by barge to many markets.

There are other good manufactured aggregates available in other areas, but I am not very familiar with the details of the products.

Along the East coast, volcanic Pumice from Greece is also commonly used.

Good luck!!

Dick
 
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Old 09-23-05, 05:55 PM
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I called a ready mix plant today and talked to an engineer. Lightweight from their plant weighs 125 pounds to the cubic foot. A lot more than I expected. Their regular mix weights 150 pounds to the cubic foot. They can make lightweight lighter by foaming it up. When they do that they put air into the concrete, he also mentioned bits of Styrofoam. When they do that the concrete will not give off the heat like it should. I have brought home concrete test cylinders for use in a retaining wall. Once in awhile I will run across one of lightweight. The lightweight ones are a lot lighter than the others are. That is why I thought lightweight was a lot lighter than regular concrete. "Big surprise" The dead load of a floor is 10 pounds, since I doubled up every other floor joice I now have a dead load of 15 pounds. The live load is 45 pounds in a standard floor; mine should be 60 pounds. I was told that I could use some of the live load that I don't need and put it toward my dead load. I hope he knows what he is talking about.
 
 

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